GeForce 9800 GTX SLI review (BFG) -
3 - Power, Noise and Heat

Power consumption

Alright then, we already installed the card into our test-system and will monitor a couple of pretty important items.

We'll now show you some tests we have done on the overall power consumption of the PC. Looking at it from a performance versus wattage point of view the power consumption is not as bad as I expected it to be, yet it quite is a lot. One card according to our findings will consume close to ~150 Watts.

The methodology is simple: have a wattage monitor keeping a close eye on power consumption during our entire test-session. This device will register the maximum wattage pulled from the wall power outlet. You are not looking at the power consumption of the graphics card, but the consumption of the entire PC. We had a total system wattage peak at roughly 420 Watts with two 9800 GTX cards installed, which is quite a lot.

The new G92 65nm cores are more power efficient than the G80 generation. So while power consumption is high, it's not at all higher then the last gen 8800 GTX product + we have more performance. NVIDIA claims a maximum of 156W peak.

So here's my power supply recommendation:

A single GeForce 9800 GTX requires you to have a 450 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total) at least 25-30 Amps available on the 12 volts rails.

A second GeForce 9800 GTX installed is another ballgame though; on this system it requires you to have a 750 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total) at least 45 Amps available on the 12 volts rails.

A third GeForce 9800 GTX requires you to have a 1000 Watt PSU, with recommended 55 AMPs available on the 12 volts rails.

There are many good PSU's out there, please do have a look at our PSU reviews as we have loads of recommended PSU's for you to check out in there. What would happen if your PSU can't cope with the load?:

Noise Levels coming from the graphics card

When graphics cards produce a lot of heat, usually that heat needs to be transported away from the hot core as fast as possible. Often you'll see massive active fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. I'm doing a little try out today with noise monitoring, so basically the test we do is extremely subjective. We bought a certified dBA meter and will start measuring how many dBA originate from the PC. Why is this subjective you ask? Well, there is always noise in the background, from the streets, from the HD, PSU fan etc etc, so this is by a mile or two not a precise measurement. You could only achieve objective measurement in a sound test chamber.

The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBa level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement. Frequencies below 1kHz and above 6kHz are attenuated, where as frequencies between 1kHz and 6kHz are amplified by the A weighting.

TYPICAL SOUND LEVELS

Jet takeoff (200 feet)

120 dBA

Construction Site

110 dBA

Intolerable

Shout (5 feet)

100 dBA

Heavy truck (50 feet)

90 dBA

Very noisy

Urban street

80 dBA

Automobile interior

70 dBA

Noisy

Normal conversation (3 feet)

60 dBA

Office, classroom

50 dBA

Moderate

Living room

40 dBA

Bedroom at night

30 dBA

Quiet

Broadcast studio

20 dBA

Rustling leaves

10 dBA

Barely audible

Not too bad, the reference cooler though you can hear yet remains silent. We measure roughly 40 DBa from the (entire) test system. The low noise design definitely works fine. This is in idle though.

When we start to stress and heat up the GPU cores the RPM of the fans will increase, still not bad bad but our results end at a 44 DBa weighing which is noticeable, but not annoying.

BFG GeForce 9800 GTX core temperatures

Let's have a look at the temperatures these single slot design coolers produce. As always we measured at a room temperature of 21-22 Degrees C.

100% reference means 100% the same temps. The card in it's default configuration will get close to 75 Degrees C / 167 F on the temperature. Mind you that with two cards, you definitely should get some proper ventilation in your PC.